[AR] Re: Lubricant for cryogenic Valves
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 19 Feb 2023 23:29:10 -0500 (EST)
On Sun, 19 Feb 2023, roxanna Mason wrote:
Henry, I was referring to using graphite in liquid methane and other
fuel/non oxidizer applications, vacuum wasn't specified.
Yes, but the point is more general: graphite's lubricating properties are
fragile in extreme conditions, and you have to be careful about how you
treat it. Not ideal.
(Trouble getting air out of the methane plumbing? Just pull a vacu...
Oops.)
But Teflon/PTFE and other relare fluorinated elastomers have been
aforementioned and are suitable for light loading applications with
glass filled for moderate loading.
With some cautions of their own -- notably *very* high coefficients of
thermal expansion/contraction compared to metals. (One advantage of the
glass-fiber-filled versions, even in light-load applications, is that the
fiber tends to restrain the Teflon somewhat.)
MoS2 is messy and never used for LOx service.
There seems to be some disagreement on that. :-)
Henry
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